Radio direction finder



Nov. 21, 1950 F. DE FRL-:MERY 2,530,600

RADIQ DIRECTION FINDER Filed July 2, 1946 Pau-Pau PUSH-PULL IMPL/FIF? FILTER DETECTR FILTER IN VEN TOR.

AGENT.

Patented Nov. 21, 1950 2.530,6@ nADromnECTIoN ENBER;

.Frank De.. Eremem. Eindhoyom. Netherlands. signor to Hartford National Bank and Trustl Company, Hartford,l Conn., astriistee Applicationl July 2A; ,1946, ,SerialNQ.-. 680,901: In .the Netherlands Apri1..1 2,.19.43.

Section 1, Public'Law 690, AugustgS, 1946" Patent expires April- 12; 17963:

1.3 Glamss, l1

' The invention relatesto @method oe determineh ing. a direction locat ol;` in. at determined.- plane? by means; of the ongle..1 which. the..Y direction to. be, cir-iterrninedA makes. withV a. known directionY of.-

orientation loca-tedthis plane. For determining the azimuth on, board. shipsD it is. known; to. utilize-I tWo highffrequencyeelds.

whichY are-emitted in suehzmanner that` the phase. of the'oscillationv obtained after detection of thek one. no1@ is independent of. direction Whereas the. phase-of the oscillation obtained after detection. or the other acid-is dependent oridirooton Whilst furthermore. in one. determined direction (direc:V tion of orientation) the two oscillationshave the. same. phase., Irithis oase the phase` angle. between the twooscillations obtained after. detetf-A tion. corresponds. tothe, azimuth..

Ithasalso been Yproposedto .utilize this method, 'for` the determination of. the. elevation.

The vsaid known methodhas the drawback that the azimuthcannot be determined- With great'accuracy since thevery exact measurement of phasev angles entails diculties.

The inventionhas for itsfobjectf. to obviate the said drawback and to provide a methodof deter-.1. mining a directionflocatedinfa determined plane by means of theanglev which the direction to be determined makes with a direction of orienta.- tion located in thisglanekwith which it is possible to attain a very great accuracy According to the invention, a measuring charactersticwhioh is a. measurefor the' angle is. derivedv fromV thev relative position of twoy harmonically related oscillations; o?` diierent frequencies (w and uw) which occur in the plane passingthrough the directionof' orientation and through the direction to be determined` in` such mannerthat the twooscillationshaveV a phase which corresponds tothe angle e.

Erom the two oscillationsY is preferably derived a. measuring characteristic which is proportional to sin mib or isy determined by (nl-1).

A particular advantage which=can beebtainedl with the method according to the invention, resides in that the two oscillations w and 'nw can be transmitted While being modulated on the same carrier-Wave,

' A, detailed explanationA follows with reference-` to the accompanying drawingI forming a part of4 the specification and: in which:

Figure 1 is a block` diagram of a transmitter according to the inve-ritiene Fig. 2 is a block diagram of a receiver accordme` '60. the; invention.;- and EiefI is diaeram; of,T an.. indication.; nr.Colleonii on the indicating device of an embodiment off'the-g receiver shown; in Eig. 2.-

` Eig. 1; represents diagrammatically one embedimelltpta beacondevicersuitable for carnying out the-.method accordingrto the-invention. 1n. this beaconl devicethel oscillations.. generated by aL high-frequency oscillator l are supplied, asthe` casemaybe Via. a frequency multiplier 2' ande a high-trequency amplifier-T- 3; toa nal: amplica. lfQIl.: Stage-4 and-lio. tivo push-pull modulators 5;.. and 5.` these; twoV modulators the` high-ira. quency.. oscillations altay modulated; with carrier-f. Wavegsuppressi by. two oscillations w. and; nw bleween. whchi exists. ahar-monic relation. The modulating oscilla.. on. with.I the frequency w is generatedeby mea-neef anoscillator l'andis supe.. plied; en theorie hand, via a, fundamental frequency amplierv i8 andi a furtherY amphi-'len 8i the modulator: antigen theother hand,A via- Y the other handvthrouga; phase-displacing; device 9 which brings about: an phase-displacementof; 90?-, andy viaan ampli.-` er l Ekto the Y.pushr-.loullzmodulator 6": The moduf.Y lating;oscillationiwith thelfrequency no. is de-., rived, by meanSzQf-.afreouency multiplierl H; from? therosoilletione generatedaby the oscillator l andf is supplied, on the one hand,..through;a lowffre. fluency ampliel: l0 te' the.; modulator Si and; on phase.fdisplacing` de\ vice l2 andtheom die 8 to-themodulator.5;'

'Ehe-beacon deviceaooordine-*to Fig: r com; prises .furthermore tour. tioaledinole-aerials; t3.; 14;. Hondt. It, whioharefarranged ntheaneularz Reime of a, Sonore er-dft whionareperpendicular to-.the-fplane of-.thefolrawine whilst. an aerial il .i is arranged in the centre of the square and is page., allel to the other aerials@l The oscillations set upin the output circuit of the nal amplier 4 are supplied tothe central aerial. ll. whereas the. oscillations, oet unY in. the, output. circuits.. of duletors. 5. and. e are supplied in antenhase tothe. aerials. l5; andn I4, I'6 respectively which are located in the diag onal points of the sulla-rde.. In the preferred embodiment of the invention, the carrier wave is V. transmitted to the receiving devices by means of Central aerialy ltinorderzthatzthe advantages,

ot. sunpreeeed. carriertitiller-r1..ieeionl ma be:` Seeuredfoethe .e ostiliationsSetonr .e modulators 5 an r., edi device, the.: aerial's, a

of 90 between the two aerials, owing to which a high-frequency eld modulated by the two oscillations w and nw is radiated in such manner that the phase of the oscillations obtained after detection is dependent on direction in a horizontal plane. With the above described antenna system, the radiation patterns of the high frequency fields will essentially be of cardioid shape; however, the exact shape of the radiation pattern is immaterial to the eX- tent that any other radiation pattern having a directional characteristic may be employed. It is only essential that the antenna system produce a rotating radiation pattern having some directivity and that the two superimposed rotating patterns be modulated at harmonica-Hy rotating frequencies so that the phase angles between the radio frequency field in any givefn direction is proportional to the angle between that direction and the direction at which the fields are in phase.

By means of a phase-displacing device l2 it may be achieved that the two oscillations w and no which are obtained after detection pass simultaneously through zero in a determined direction located in the said plane (direction of orientation).

In an arbitrary direction which makes an angle with the direction of orientation, there are consequently obtained after detection two oscillations of which the one is proportional to sin. (wt-) and the other is proportional to sin. (mut-).

The angle to be determined may be derived from these two oscillations .in different ways, for example by multiplying the oscillations with the lowest frequency which is obtained after detection, n times in frequency, owing to which we obtain an oscillation which is proportional to sin (nw1f-n). By determining the phase angle between the oscillation multiplied in frequency and the oscillation with the highest frequency which is obtained after detection and which is proportional to sin (mut-) we obtain a measuring characteristic which is determined by (nf-1) Whereas with the known measuring method the angle was measured.

With the same measuring equipment we consequently obtain a larger deflection.

It is true that in measuring small angles [3 with the aid of the known measuring equipments it would be possible in some cases to obtain the same indication with the use of an amplifier with the amplification factor n-l, but this entails the drawback that after'having passed through the angle the pointer leaves the scale whereas with the device according to the invention the pointer, after having passed through the angle .ceived by an aerial are supplied to a highfrequency amplier 2l which is connected in cascade with a frequency -changer 22, an intermediate-frequency amplifier T23 and a detector 24.

Preferably, an automatic gain control voltage is derived from detector 24 and is applied to intermediate-frequency amplifier 23 in order to obtain an indication which is independent of the amplitude of the incoming signal, although this feature may be omitted if it is not desired. Also, it is preferable that intermediate-frequency amplier 23 be designed to incorporate a limiting feature as well as to provide the necessary gain at intermediate frequency. In the output circuit of the detector are obtained two oscillations, of which the one is proportional to sin (wt-) and the other is proportional to sin (not-), For

deriving the angle [i from these two oscillationsuse is made in the form of construction shown in Fig. 2 of a cathode-ray tube 29 which comprises two deflecting members 2B, 23 which bring about a deection of the beam in two mutually perpendicular directionsthe two received oscillations being supplied to the said two deiiecting members respectively. The oscillations with the highest frequency (nw) which are set up in the output circuit of the detector 24 are supplied via a filter 25 to deiiecting plates 29 whereas the oscillations with the frequency w are supplied via a iilter 2l to horizontal deflecting plates 28 of cathode-ray tube 29. In this way there is produced on the screen of the cathode-ray tube a stationary Lissajous-iigure whose X-axis is proportional to sin (wt-) whereas the Y-axis is proportional to sin (mut-). One example of such a Lissajous-figure is shown in Fig. 3, this figure being obtained in a direction to be determined if n=8.

The ordinate of the point of intersection of the Lissajous-curve and the Y-axis, which indicates the instantaneous value of the oscillations with the frequency nw at the moment when the oscillation with the frequency w passes through zero, yields a measuring characteristic which is proportional to sin (1L-DIS and which is consequently a measure for the angle ,8, for if,

X=A sin (wt-) :0, then is also sin 11. (wt) =0 cos (wt-)=1 and cos n (wt-) .-.1 It follows therefrom that the maximum value of the measuring characteristic is attained, whereupon with the increase of the measuring characteristic decreases to a minimum value and then, when attains again the value 0 occurring in the direction of orientation. owing to which the device re- `5i turns automatically to the startingpoint, whichv isreneateii each. time with the. increase of. c after If' with. the method according tothe invention a high factor n is utilized,v a proper deflection is obtainedv evenv when determining directions which include a. small angle c with the direction of orientation,- so that the angle ck can bedetermined. with great accuracy.4

With the above-described device there were obtained two oscillations. with harmonically related frequencies which were. proportional to sin (nt-) and to sin (not-) respectively, since with the transmitting device describedwith reference toFig. 1 both for the oscillations with the, frequency w and for the oscillations with the, fleifiuency uw the aerialsV I3 to I6 are fed in such mannerY that the current in. the aerial |3 leads with respect to the currents in theother aerials. If,4v however, the phase-displacing devices .li` and |12. are provided in, such manner that, for exarnple.,V for the. frequency c` the current. inthe aerial I3 leads and for the frequency nw lags behind with respect to the currents in the other aerials, we obtain after detection two oscillations which are proportional to sin (wt-),- andto sin (net-H3) respectively. From the relative position of the two oscillations may be derived in this case a measuring characteristic which either is .determined by (n4-Dc or is proportional to sin (1H-1m since sin (nef-i-) may be represented; by {sin mar/3) (n+1) What I claim is:

v l. A method of establishing a bearing by radio means, comprising the steps of' radiating a first radio frequency field of a predetermined pattern modulated a-t a given frequency and rotating at the angular velocity of said given frequency, radiating a second radio frequency eld of the same pattern modulated at a second frequency harmonical'ly related to said given frequency and rotating at the angular velocity of said second frequency,and synchronizingsaid rotating radio frequency fields to provide an in-phase relationship-` in agiven azimuthal direction whereby saidA bearing withv respect to said given aZirnuthal direction is established proportional to the phase difference between said first and said second radio frequency fields. v,

v2. A method of establishing a bearing by radio means, comprising the steps of radiating a first radio frequency field of a predetermined p attern modulated at a. given frequency and rotating at the angular velocity of said rgiven fre'- quency, radiatingv a second radio frequency field of the saine pattern modulated at a second frequency harmonically related to 'said` given frequency and rotating at the angular velocity of said second frequency, and synchronizing said rotating radio frequency fields to provide an in-v phase relationship in a. given azimuthal directionv whereby said bearing with respect to. said given, azimuthal direction is proportional to the arc. sine ofl the phase angle between said first and said second radio frequency fields divided by the quant-ity (nil) where n is the order of the harmonic relationship of :fthe modulating frequencies.

3. Amethod of establishing a bearing by radio meanavcomprising the steps yof radiating a first,

radio frequency field of a cardicid pattern modulated `'at a given frequency and rotating at the angular velocity of said given .frequencyr radiatfrequency, and: synchronZili,saidk rotating ral o:

ing a second radio frequency field.' or a cardioid:

pattern. modulated at. a second; frequency harz-i;

monicauy related to: said givn .frequency and rotatingfat the angular velocity of said; seco frequency fields to provide an insphase relatimt` shipfin a given; azimuthel direction whereby' S Si' bearing with respect to said given azimuthal die rection is. equal to the phase angle between said first and said second radio frequency fields. di-V videdl by the; factor (will Where n is the order of theharmonic relationship of the modulating.: frequencies.

4.l A method of establishingl a; bearing by' radici means, coinprisingthe steps of radiating a first radio frequency field of a predetermined pattern modulated atfa. given frequency and rotating a,` the angular velocity. of said given frequen y, radiating a second radio frequency field of;` the same pattern modulated: ata second. frequency" harmonically related toi said given frequency and rotating. at the angular velocity of said secondifrequency` and in the same direction as said first; radio frequency field, and synchronizingl said rotating radio frequency fields to provide an ine phase relationship in a givenv azimuthal direction whereby said bearingY with respect to said given azimuthal direction is. equal to. the` phase angle: between said first and said'. second radio fre-- quency fields divided by the factor (nel) where n, is the .orderof harmonicV relationship. ofthe modulating frequencies.

`5. A method of establishing a bearing by radio means, comprising the transmission ofv radio siga nals providing an indication of said bearing comprising the stepsof radiating; a first radici frequency field of a Vpredetermined pattern modulated at a given frequency and rotatingatl the angular velocity of said givenv frequency, radiating a second radio frequency fieldof the same pattern modulated at a second frequency' harmonically related to said given frequencyand` rotating at the angular velocity of said secondi frequency, and synchronizing said rotating radio frequency fields to provide an inephase relation-f ship. in agis/'enl azimuthal directiony whereby said bearing with respect to. said given azimuthal di', rectionis established proportional' to the phase difference between said first and said second radio frequency fields, andv the` detection of saidy radio signals comprising the steps of receiving said signals, -rectifying said signals, filtering they rectified component of said signals `to produce ay first voltage having amplitude variations corres spond-ing to said `firstinodulating frequency and` a second. voltage having amplitude variations corresponding to said harmonic modulating frequency, and measuring the phase anglelzietvveen` said first and said second voltages thereby determining said bearing.

6. vA method of establishinga lbear-ing by radio means, comprising the transmission of radio sig.-n nals-V providing an indication of said bearing. comprising the steps of radiating a first radio frequency'fieldrof apredetermined pattern inodulated at a given frequency .and rotating at the angular velocity of said .given frequency, radi-f' atingfa. second radio frequency field of the same., pattern-modulated .at a. second frequency hare. monically relatedlto said given-frequency and ro.- tating -at'the angular velocityof said second fre.-

quency, and synchronizing said rotating radiofrequency :fields .to :provide an in-,phase relations ship in a given azimuthalrdirection whereby said`V` bearing `with respect to said ,given azimuthal die rection is established proportional to the 'phase' difference between said first and said second radio frequency fields, and the detection of said radio signals comprising the steps of receiving said signals, rectifying said signals, filteringl the rectified component of said signals to produce a first voltage having amplitude variations corresponding to said first modulating frequency and a second Voltage having amplitude variations corresponding to-sai'd harmonic modulating frequency, and measuring the instantaneous amplitude of said second voltage at the time when the instantaneous amplitude of said first voltage passes through zero thereby determining said bearing.

- 7 A method of establishing a, bearing by radio means, comprising the transmission of radio signals providing an indication of said bearing comprising the steps of radiating a first radio frequency field of a predeterminedpattern modulated at a given frequency and rotating at the angular velocity of said given frequency, radiating a second radio frequency field of the same pattern modulated at a second frequency harmonically related to said given frequency and rotating at the angular velocity of said second frequency, and synchronizing said rotating radio frequency fields to provide an in-phase relationship in a, given azimuthal direction whereby said bearing with respect to said given azimuthal direction is established proportional to the phase difference between said rst and said second radio frequency fields, and detection of said radio signals comprising the steps of receiving said signals, rectifying said signals, filtering the rectified component of said signals to produce a first voltage having amplitude variations corresponding to said first modulating frequency and a second voltage having amplitude variations corresponding to said harmonic modulating frequency, and producing an oscillogram of said first and said second voltages at a phase displacement of 90 thereby providing a direct indication of said bearing.

8. A transmitter for establishing a bearing by radio means comprising means to generate a first and a second oscillation of predetermined frequency value, means to modulate said first oscillation by a given frequency, means to modulate said second oscillation by a second frequency harmonically related to said given frequency, means responsive to said first modulated oscillation and said second modulated oscillation to produce directional radio frequency fields radiating into space and rotating at angular velocities corresponding to the respective modulating frequencies, and means to shift the phase relationship of said first and said second modulating frequencies to produce an in-phase relationship of said rotating radio frequency fields in a given azimuthal direction thereby to establish said bearing with respect to said azimuthal direction as the phase angle between said given frequency and said harmonically related frequency.

9. A transmitter for establishing a bearing by radio means comprising means to generate a first and a second oscillation of predetermined frequency value, means to modulate said first oscillation by a given frequency, means to modulate said second oscillation by a second frequency harmonically related to said given frequency, means responsive to said first modulated oscillationand said second modulated oscillation to produce directional radio frequency fields radiating into `space and rotating at angular vephase lating frequencies, and means to shift the phase 1 relationship of said first and said second modulating frequencies to produce an in-phase relationship of said rotating radio frequency fields in a given azimuthal direction, said radio frequency fields occurring in a plane passing throughv said given azimuthal direction and said bearing, thereby to establish said bearing with respect-to said azimuthal direction as the phase angle between said given frequency and said harmonically related frequency.

10. A transmitter for establishing a bearing by radio means, comprising means to generate a wave of carrier frequency, means to generate an oscillation of a given frequency, means to generate a second osciliation of a frequency harmonically related to said given frequency, a first phase shifting circuit element, means to apply `said second oscillation to said first phase shifting circuit element, a first balanced modulator,

means to apply said carrier wave, said first oscillation and the output of said rst phase shifting circuit element to said balanced modulator to v suppress said carrier wave and generate side-band frequencies corresponding to said first oscillation and said phase-shifted harmonic oscillation, a second phase shifting circuit element, means to apply said given oscillation to said second shifting element, a second balanced modulator, means to apply said carrier wave, said harmonic oscillation and the output of said second phase shifting circuit element to said second balanced modulator to suppress said carrier wave and produce side-band frequencies corresponding to said harmonic oscillation and the phase-shifted given oscillations, an aritenna system including first and second spaced' pairs of radiators, said first pair being perpendicularly disposed with respect to said second pair, means to couple said first and said second balanced modulators in phase opposition to the radiators of said first and second pairs respectively of said antenna system to radiate into space two rotating directional radio frequency fields having a phase relationship therebetween, and means to adjust said first phase shifting circuit element to produce an in-phase relationship of said rotating radio frequency fields in a given azimuthal direction thereby to establish said bearing with respect to said given azimuthal direction proportional to the phase angle between said rotating radio frequency fields.

l1. A transmitter for establishing a bearing by radio means, comprising an antenna system having a central radiator and a plurality of pairs of diametrically opposed cooperating radiators sym-' I metrically arranged around said central radiator, means to generate a wave of carrier frequency, means to apply said wave to said central radiator to transmit said carrier frequency wave omni-l directionally, means to generate an oscillation of a given frequency, means to generate a second oscillation of a frequency harmonically related to said given frequency, a first phase shifting circuit element, means to apply said second oscillation lto said first phase shifting circuit element, a

first balanced modulator, means to apply said carrier wave, said first oscillation and the output of said first phase shifting circuit element tol said rst balanced modulator to suppress said carrier wave and generate side-band frequencies corresponding to said first oscillation and said' phase-shifted harmonic oscillation, means to couple said first balanced modulator in phaseA opposition to the radiators of the rst pair of said plurality of pairs of cooperating radiators, a second phase shifting circuit element, means to apply said given oscillation to said second phase shifting element, a second balanced modulator, means to apply said carrier wave, said harmonic oscillation and the output of said second phase shifting circuit element to said second balanced modulator to suppress said carrier wave and produce side-band frequencies corresponding to said harmonic oscillation and the phase-shifted given oscillation, means to couple said second balanced modulator in phase opposition to the radiators of the second pair of said pairs of cooperating radiators, thereby to radiate into space two directional radio frequency fields rotating about the locus of said central radiator and having a phase relationship therebetween, and means to adjust said first phase shifting circuit element to produce an in-phase relationship of said rotating radio frequency fields in a given azimuthal direction thereby to establish said bearing with respect to said given azimuthal direction proportional to the phase angle between said rotating radio frequency fields.

12. A receiver for determining a bearing transmitted by radio signals having values proportional to the phase angle between a first radio frequency field modulated at a given frequency and rotating at the angular velocity of said given frequency and a second radio frequency field modulated at a second frequency harmonically related to said given frequency and rotating at the angular velocity of said second frequency, said rotating radio frequency fields being synchronized to provide an in-phase relationship in a given azimuthal direction, comprising means to receive said signals, means to detect said signais, means responsive to said detected signals to produce a first voltage having amplitude variations corresponding to said first modulating frequency and a second voltage having amplitude variations corresponding to said harmonic modulating frequency, a cathode ray tube having horizontal and vertical deiiection elements, means to apply said rst voltage to the horizontal deflecting elements of said cathode ray tube, and means to apply said second voltage to the vertical deflection elements of said cathode ray tube, thereby to determine said bearing.

13. A receiver for determining a bearing transmitted by radio signals having values proportional to the phase angle between a first radio frequency field modulated at a given frequency and rotating at the angular velocity of said given frequency and a second radio frequency field modulated at a second frequency harmonically related to said given frequency and rotating at the angular velocity of said second frequency, said rotating radio frequency fields being synchronized to provide an irl-phase relationship in a given azimuthal direction, comprising means to receive said signals, means to detect said signais, means responsive to said detected signals to produce a first voltage having amplitude variations corresponding to said first modulating frequency and a second voltage having amplitude variations corresponding to said harmonic modulating frequency, a cathode ray tube having horizontal and vertical deflection elements, means to apply said rst voltage to the horizontal deecting elements of said cathode ray tube and to apply said second voltage to the vertical deection elements of said cathode ray tube to measure the instantaneous amplitude of said second Voltage at the time when the instantaneous amplitude of said first voltage at the time when the instantaneous amplitude of said first voltage passes through zero, thereby to determine said bearing directly.

FRANK DE FREMERY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,815,246 Englund July 21, 1931 1,922,677 Greig et al. Aug. 15, 1933 2,121,024 Diamond June 21, 1938 2,198,113 Holmes Apr. 23, 1940 2,252,699 vByrne Aug. 19, 1941 2,253,958 Luck Aug. 26, 1941 2,297,395 Erben Sept. 29, 1942 2,377,902 Relson June 12, 1945 2,394,157 Earl Feb. 5, 1946 2,422,110 Luck June 10, 1947 2,483,557 OBrien Oct. 4, 1949 

